PTLs 1 and 2 propose the addition of an organic or inorganic acid to reduce the gelation of a positive electrode mixture for a positive electrode of a lithium ion secondary battery. In PTL 1, maleic acid, citraconic acid, and malonic acid are used in positive electrode mixtures. In PTL 2, acids such as acetic acid, phosphoric acid, and sulfuric acid are used in positive electrode mixtures.
PTL 3 proposes the use of a polymer containing no structural units derived from vinylidene halides as a binder for an electrode of a sodium ion secondary battery including a sodium-containing transition metal compound as an electrode active material.